Conventionally, vehicle seats have been generally produced by embedding and integrally molding a metallic wire as an insert material for stabilizing the shape in a seat main body made of polyurethane. In recent years, from the viewpoints of weight saving and cost reduction of vehicles and the like, there has been proposed a structure in which polyurethane and a polyolefin-based resin foam-molded body are combined (refer to Patent Document 1, for example). The invention described in Patent Document 1 has an advantage in that, by using a polyolefin-based resin foam-molded body which is higher in strength than polyurethane for a vehicle seat, the polyolefin-based resin foam-molded body constitutes a core material for stabilizing the seat shape, thereby eliminating the need for a metallic wire that would have been essentially required for stabilizing the shape as a core material in a structure made of only polyurethane. However, a U-shaped hook is necessary to attach the vehicle seat to the vehicle, and the metallic wire needs to be left as an anchor material for fixing the U-shaped hook to the vehicle seat.
Meanwhile, to integrally mold the metallic wire and the polyolefin-based resin foam-molded body, the amount of the metallic wire embedded in the foam-molded body may be smaller because the seat becomes more lightweight. In that case, however, the bonding between the polyolefin-based resin foam-molded body and the metallic wire is weak, and the metallic wire would come off the foam-molded body under a strong impact and the seat might not satisfy safety standard for passengers (anti-submarine). To improve the seat in resistance to impact, the metallic wire embedded in the foam-molded body needs to be made thick, long, or plate-like to increase the strength of the bonding between the metallic wire and the foam-molded body. Therefore, the shape of the metallic wire depends on the shape of the vehicle seat and may take on various shapes. For example, the wire may be annular or the wire may be exposed from the foam-molded body.
As a method for fixing the wire to a mold for integrally molding the foam-molded body and the metallic wire, Patent Document 2 proposes a method by which the outer wall of a lower mold part with a groove for attaching the metallic wire is partially slid by a spring in integral molding of the urethane resin foam-molded body and the metallic wire to allow the metallic wire to be readily installed in the mold when the mold is opened. In addition, Patent Document 2 also proposes a structure in which the metallic wire is fixed in a predetermined position when the mold is closed, and after the molding, the mold release is facilitated by opening the mold.
In addition, there has been proposed a structure for integrally molding a polypropylene-based resin foam-molded body and a metallic wire in which a wire fixing tool provided at a lower mold part is slid by a spring so as to provide almost no clearance between the metallic wire and the mold, and the mold is not completely closed but leaves a slight clearance even at a thin-walled portion into which polypropylene-based resin pr-expanded beads are hard to be filled, so that the polypropylene-based resin pre-expanded beads can undergo cracking-filling to be filled into the thin-walled portion, and when the mold is completely closed after the filling, the wire is fixed to a predetermined position (for example, refer to Patent Document 3).